It is now well established that the plasma membrane is composed of various types of microdomains containing unique sets of proteins and lipids. Among these, cholesterol- and saturated-lipid-enriched microdomains known as lipid rafts have been the subject of much interest and debate across several disciplines of biology. We and several other groups demonstrated that lipid rafts play important roles in HIV-1 assembly and entry. We have explored the possibility that cholesterol-depleting and cholesterol-binding compounds inhibit HIV-1 replication. Our ongoing studies with amphotericin B methyl ester (AME), a cholesterol-binding polyene fungal antibiotic, have revealed a novel mechanism of escape from an HIV-1 entry inhibitor. The molecular basis for this escape will be defined in future studies. [Corresponds to Freed Project 3 in the April 2007 site visit report of the HIV Drug Resistance Program]